Tidal motors making use of the natural rise and fall of ocean tides are generally known to be useful for powering energy generating devices or for directly performing other useful work. Such prior art systems are known to use floats that rise and fall with the tides and to utilize the motion of the float as input energy to a motor of some kind that may drive an electrical dynamo. The motor itself may be hydraulic, pneumatic, or mechanical in nature, and often some form of energy storage system is provided to insure constant flow of power between the tidal changes.
While it is generally recognized that a large hollow float can be used to generate an appreciable upward buoyant force equivalent to the mass of the water displaced by the float less the weight of the float assembly, and that such force can be put to useful work, the prior art has failed to deal effectively with the fact that this force no longer exists during an outgoing tide, since the float element then can only generate a maximum force equivalent to its empty weight.
Prior art systems have attempted to work around this problem by using various pump arrangements for cyclically filling the float with water to sink it, then discharging the water from the float so that it is buoyant again. Obviously this represents a substantial consumption of the energy that is being derived from the tidal motor in the first place and is inefficient.